As is well known, in the case where a synchronous machine having a permanent magnet, as a magnet-field magnet, is controlled by a synchronous machine control device having an electric-power conversion means such as an inverter, a temperature rise due to energization of the armature winding of a synchronous machine, an iron loss in the synchronous machine itself, or the like causes a so-called “demagnetization” phenomenon in which the intensity of magnetization of the magnetic-field permanent magnet, i.e., the magnetic flux is reduced; furthermore, when the allowable temperature is exceeded, a so-called “irreversible demagnetization” phenomenon is caused in which even when the temperature falls down to the normal temperature, the magnetic flux does not return to the state at a time before the demagnetization is caused. Accordingly, it is required that when a synchronous machine having a permanent magnet as a magnetic-field magnet is controlled, at least the temperature of the permanent magnet is suppressed at a temperature lower than the allowable temperature at which irreversible demagnetization is caused. However, due to a space problem caused by the structure of the synchronous machine, a case protecting the outside of the synchronous machine, or the like, it is difficult to directly mount a temperature detection device on the permanent magnet; accordingly, there is required a technology for indirectly measuring or estimating, with some sort of method, the temperature of the permanent magnet or the magnetic flux related to the temperature of the permanent magnet.
As an example of synchronous machine control device that solves these problems, there exists a conventional device (for example, refer to Patent Document 1) in which based on information items about the current, the temperature, and the rotation speed obtained from a current sensor that detects the current to be exchanged between the inverter and the armature winding, a temperature sensor that detects the temperature of the armature winding so as to correct the resistance value of the armature winding, and a magnetic pole position sensor that detects the magnetic pole position of the magnetic-field magnet, respectively, the magnetic flux that departs from the magnetic-field permanent magnet and is interlinked with the armature winding is obtained by a magnetic flux observer consisting of a model of the synchronous machine (electric rotating machine) and a proportion integrator. As another example of similar control device, there exists a conventional device (for example, refer to Patent Document 2) that has a means for detecting the value of a phase-difference angle δ between the induction voltage generated by a permanent magnet and the terminal voltage and outputs magnet temperature information, with reference to the phase-difference angle δ at a reference temperature and the detected phase-difference angle δ and based on a magnet temperature table.
As another example of the similar control devices, there exists a conventional device (for example, refer to Patent Document 3) in which in the control utilizing a rotating-two-axis (d-q axes) coordinate transformation, a q-axis voltage operation amount at the time when no demagnetization is caused in an permanent magnet is held as a map and then a demagnetization amount is calculated based on a q-axis voltage operation amount, which is the output of the PI control unit at the time when a synchronous machine is current-controlled through proportional integral (PI) control, the q-axis voltage operation amount held in the map (when no demagnetization is caused in the permanent magnet), and a rotation angular-velocity ω.
Each of Patent Documents 4 and 5 discloses an example of technology in which based on a voltage command for a synchronous machine and an armature current, the rotor position of the synchronous machine is estimated through a calculation.